Reload: Don't free the saved class table while another thread may be reading it.

runtime/vm/isolate.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/isolate.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 #include "platform/assert.h"
 #include "platform/text_buffer.h"
@@ skipping 1091 matching lines @@
     isolate->heap()->CollectAllGarbage();
     VerifyCanonicalVisitor check_canonical(thread);
     isolate->heap()->IterateObjects(&check_canonical);
   }
 #endif  // DEBUG
   return success;
 }
 
 
 void Isolate::DeleteReloadContext() {
+  // Another thread may be in the middle of GetClassForHeapWalkAt.
+  Thread* thread = Thread::Current();
+  SafepointOperationScope safepoint_scope(thread);
+
   delete reload_context_;
   reload_context_ = NULL;
 }
 #endif  // !PRODUCT
 
 
 void Isolate::DoneFinalizing() {
   NOT_IN_PRODUCT(
     if (IsReloading()) {
       reload_context_->FinalizeLoading();
@@ skipping 1772 matching lines @@
 void IsolateSpawnState::DecrementSpawnCount() {
   ASSERT(spawn_count_monitor_ != NULL);
   ASSERT(spawn_count_ != NULL);
   MonitorLocker ml(spawn_count_monitor_);
   ASSERT(*spawn_count_ > 0);
   *spawn_count_ = *spawn_count_ - 1;
   ml.Notify();
 }
 
 }  // namespace dart